linux-kernel - Re: [PATCH v3 02/14] thermal: core: Rearrange checks in thermal_bind_cdev_to

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Message-ID: <8744a789-0424-0cc6-7cb1-b7c9b17f56cc@huawei.com>
Date: Wed, 21 Aug 2024 17:44:05 +0800
From: "lihuisong (C)" <lihuisong@...wei.com>
To: Daniel Lezcano <daniel.lezcano@...aro.org>, "Rafael J. Wysocki"
	<rjw@...ysocki.net>
CC: LKML <linux-kernel@...r.kernel.org>, Lukasz Luba <lukasz.luba@....com>,
	Zhang Rui <rui.zhang@...el.com>, Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v3 02/14] thermal: core: Rearrange checks in
 thermal_bind_cdev_to_trip()


在 2024/8/21 17:28, Daniel Lezcano 写道:
> On 21/08/2024 10:49, lihuisong (C) wrote:
>
> [ ... ]
>
>>> -    list_for_each_entry(pos2, &thermal_cdev_list, node) {
>>> -        if (pos2 == cdev)
>>> -            break;
>>> -    }
>>> +    lockdep_assert_held(&thermal_list_lock);
>>> -    if (tz != pos1 || cdev != pos2)
>>> +    if (list_empty(&tz->node) || list_empty(&cdev->node))
>> The old verification is ensure that tz and cdev already add to 
>> thermal_tz_list and thermal_cdev_list，respectively.
>> Namely, tz and cdev are definitely registered and intialized.
>> The check is ok for all untizalized thermal_zone_device and cooling 
>> device.
>> But the new verification doesn't seem to do that.
>
> If the tz or the cdev are registered then their "->node" is not empty 
> because they are linked with the thermal_list and cdev_list
>
> So either way is browsing the lists to find the tz/cdev or just check 
> "->node" is not empty. The latter the faster.
Assume that tz/cdev isn't intiazlized and registered to thermal_tz_list 
or thermal_cdev_list. And then directly call this interface.
>
> Did I misunderstood your comment ?
>
> [ ... ]
>